The present invention is directed to a method and apparatus for manufacturing a tamper-evident closure, and in particular, to a method and apparatus for manufacturing a tamper-evident closure having a plurality of tabs that are molded in their final position to extend radially inward and upward.
A typical tamper-evident closure comprises an internally threaded cap for engaging an externally threaded neck of a container, and a tamper-indicating assembly that is detachably connected to the bottom annular portion of the cap. When the cap is unscrewed from the container neck, the tamper-indicating assembly becomes detached from the cap and remains on the container neck so that, when the cap is replaced on the container neck, a discernible gap formed between the cap and the tamper-indicating assembly serves as a visual indication that the container has been previously opened. An example of such a typical tamper-evident closure is illustrated in FIGS. 1-3.
The tamper-evident closure 10 of FIG. 1 includes an internally threaded cap 12 and a tamper-indicating assembly 14 including a band or ring 36 detachably connected to the cap. The closure 10, which may be manufactured of a moldable plastic material such as polypropylene includes a top wall 16, otherwise referred to as a sealing surface, for extending across the open top of a container and an annular skirt or sidewall 18 integrally joined to the top wall 16 about the periphery of the top wall 16 and having a screw thread 22 formed on its inner surface 24 for engagement with a threaded container neck. The cap 12 is connected to assembly 14 by a weakened area, referred to as breakable connector means 25, in the ring 36. The breakable connector means 25 provides a severing plane normal to the closure and container axis at which the ring 36 will consistently detach from cap 12 when the closure 10 is first unscrewed. When the cap 12 is unscrewed from the container neck, the tamper-indicating assembly 14 is retained on the container neck by an annular container shoulder 28 so that continued upward motion of the cap 12 breaks the assembly 14 away from the cap 12 (See FIGS. 2-3). Those skilled in the art will understand that the direction referred to as "upward" in this application refers to a direction along the axis of a closure from the tamper-indicating assembly 14 toward the top wall 16 of the closure while downward refers to the opposite direction.
As described above, after the cap 12 has been removed from the container, the ring 36 of the tamper-indicating assembly 14 drops down on the container finish 27 so that if the cap 12 is subsequently replaced on the container, the gap between the cap and the tamper-indicating assembly 14 serves as a visual indication that the cap has been previously removed.
As illustrated in FIGS. 2-3, the container has a finish 27 with an annular shoulder 28 having an outer diameter that is larger than the diameter of the threads 29 of the container neck. The top surface 31 of the shoulder 28 is sloped downwardly and outwardly while a lower surface 30 of the shoulder 28 is tapered slightly upwardly and outwardly to provide a stop surface to limit the upward movement of the lower ring 36 to detach the ring 36 from the cap 12 when the cap 12 is unscrewed from the container neck. A neck surface 32 below the shoulder 28 has a diameter smaller than that of the shoulder 28. This difference in diameter between the neck surface and the outer shoulder diameter may be varied substantially. Herein, the neck surface 32 is illustrated as being substantially parallel to the axis of the closure. To assist in allowing the ring 36 to drop down to the position shown in FIG. 3, the neck surface 32 may be made to taper downwardly and inwardly to provide a smaller diameter at the lower end of the neck surface 32 than at the top end of the neck surface 32.
The tamper-evident closure 10 of FIG. 1 is provided with pivotal, resilient tabs 34 which, during removal of the cap 12, lock against the lower surface 30 of the annular shoulder 28 to retain the tamper-indicating assembly 14 on the container neck. The tabs 34 are preferably formed integrally with the ring 36 and preferably extend radially inward and upward from the generally cylindrical ring 36. These tabs 34 are resiliently urged against the finish 27 as they are flexed inwardly at curved ends or joints 38 where they meet the ring 36. As the cap 12 is removed, the upward force on the tamper-indicating assembly 14 tends to bow the tabs 34 inwardly against the neck surface 32 and to stiffen the tabs to cause them to engage more tightly and to grip the container neck. The closure 10 may be installed simply by screwing it downwardly onto the container neck so that the tabs 34 assist in guiding the closure 10 as it is lowered onto the container neck for installation. That is, the tabs 34 serve as a cam guiding surface of large diameter at their lower ends to center the cap 12 onto the container finish 27. Because the tabs 34 are so flexible they can readily be bent when the container and closure 10 are not axially aligned on the same vertical axis. Also during installation on a closure, the tabs 34 readily flex past large diameter tolerances on the closure finish.
Previous molding processes that have been used to manufacture tamper-evident closures such as the one illustrated in FIGS. 1-3 are not capable of molding tabs 34 in their final inward and upward folded positions. Instead, these conventional molding processes produce closures having tabs that point straight down in an unbent fashion. In order to obtain the tab configuration of FIGS. 1-3, the closure 10 is removed from the conventional molding apparatus, and a post-forming operation is implemented to bend tabs 34 radially inward and upward from the tamper-indicating assembly 14. Heat is then applied to the tab joints 38 to set the tabs 34 in the configuration of FIGS. 1-3. This post-forming step for bending tabs 34 introduces additional costs and prolongs the duration of the overall manufacturing process. Additionally, this type of post-forming step adds unwanted variability to the manufacturing process, and, as a consequence, the tamper-evident closures produced by this process are not as consistent with each other as would be desired. Accordingly, a need exists for a process of manufacturing a tamper-evident closure that avoids the extra expense and time expended by the post-forming step of bending and setting the closure tabs in their radially inward and upward position.